1. Field of the Invention
The present invention relates to a pattern identification apparatus, a pattern identification method, and a the pattern identification program in which a predetermined image is compared and collated with a predetermined pattern such as an image stored in advance to identify a predetermined pattern contained in the predetermined image. More specifically, the present invention relates to a pattern identification apparatus, a pattern identification method, and a pattern identification program capable of identifying documents, slits and the like by comparing and collating images of a variety of kinds of them with specific registered images.
2. Description of the Related Art
The payments or transfers of electricity bills, gas bills, municipal taxes (taxes, public funds), etc., are processed by using the data (the amounts of money for payments, the times for payments, etc.) described in a variety of tax documents, public fund documents and so on in banks, post offices, etc. Today, it is rare for operators to process such data described in the documents, slits, etc., by manually inputting them to machines, computers and so on, and it is becoming common to analyze and process data by using an automatic reading system which can automatically read data by means of a scanner, an optical character reader or the like.
In such a system, in order to accurately analyze the data described in a document, it is first necessary to identify the document, which is an object to be processed. For instance, there is a DP collation technique as a typical one of document identification methods. The DP collation technique is a method of comparing and collating an image of a document (i.e., image to be searched), which has been read by an image reading means such as, for example, a scanner, with a registered image while moving an image area (search area) of the document image having the same size as that of the registered image little by little relative to the registered image, thereby to search for an image of the document which matches the registered image.
FIG. 16 is a view schematically illustrating the DP collation method. As illustrated in this figure, in case where the search image comprises m dots in an X axis direction and n dots in a Y axis direction, when the DP collation method is used, collation is carried out by sequentially shifting the search area dot by dot from an upper left corner to the right and then downward line by line, thus requiring (m×n) times of searching operations. In this case, it is usual to set the search area to a wider area than the size of the registered image in consideration of displacements of the image occurring when read by a scanner. However, this search processing deals with a large mount of data and the number of search operations is also great, thus making it difficult to perform the processing at a high speed. Thus, it is considered that for the purpose of speeding up such processing, the number of data to be used and the number of processing operations are reduced by extracting characteristic portions of the registered image, thereby shortening the processing time.
However, in cases where a registered image is included in a part of the search image when search processing is carried out by using a characteristic portion of the registered image as referred to above, it is necessary to provide some margins to the area of the registered image in the search image, and perform the processing of searching for the registered image in that area while taking account of displacements caused at the time of reading the search image, etc. However, conspicuity or remarkableness of the characteristic portion of the registered image is weakened by these margins so that accuracy in the pattern recognition might be reduced, causing errors in the collation result. As a consequence, there arises a problem that reliability in the collation result is reduced.